This invention relates to a rotatable face seal for rotary machines, more especially to a bi-direction rotatable face seal with spiral grooves.
Up to now, the gas-lubricated face seal so-called dry running gas seal or dry gas seal is the most advanced seal for various rotary machines especially for turbo-compressors treating process gases. The gas-lubricated face seals can be divided into unidirectional and bi-directional seals. Typical hydrodynamic groove patterns on a sealing face of the unidirectional gas-lubricated face seals are shown in FIG. 5 and FIG. 6 of U.S. Pat. Nos. 4,212,475 and 6,152,452, respectively. Regarding the bi-directional gas-lubricated face seals, some known hydrodynamic groove patterns on a sealing face in the prior art are shown in FIG. 7 to FIG. 10. As shown in FIG. 7, U.S. Pat. No. 5,435,574 discloses a groove pattern xcex94 in trapezoidal shape, a groove pattern xcex9 in xe2x80x98xcex9xe2x80x99 shape (a Chinese character), and a groove pattern T in xe2x80x98Txe2x80x99 shape. In FIG. 8, another prior groove pattern has a xe2x80x98Uxe2x80x99 shape with varied depth. FIG. 9 of EP 0 499 370 A1 discloses a groove pattern pluralizing of the trapezoid or triangular groove patterns shown in FIG. 7. When the rotary shaft and the rotating ring rotate in a direction indicated by arrow xe2x80x98Nxe2x80x99 in FIG. 9, the groove regions may pump the sealing fluid in radial and circumferential directions. However, the hydrodynamic action caused by the groove pattern in FIG. 9 is not very efficient since each groove is comprised of one spiral side wall E, F and one circular side wall C, D. FIG. 10 of EP 0 684 413 A1 discloses a groove pattern pluralizing of the groove patterns T (double xe2x80x98Lxe2x80x99 patterns). When the rotary shaft and the rotating ring rotate in a direction indicated by arrow xe2x80x98Nxe2x80x99 in FIG. 10, the groove regions only pump the sealing fluid in a circumferential direction since the pressure peak is formed at the locations I, J, K of the groove. To avoid the aforesaid problems, a more efficient bi-direction rotatable gas-lubricated face seal with a new groove pattern is needed.
The object of the present invention is to provide a bi-direction rotatable gas-lubricated face seal with a new groove pattern that may contribute more efficient hydrodynamic action, and the sealing faces of the rotating ring and the stationary ring can maintain a non-contacting condition more steadily. The gas-lubricated face seals according to the present invention have been lab tested sufficiently and their performances are excellent.
The present invention provides a bi-direction rotatable face seal with spiral grooves comprising: a rotating ring with a sealing face sealed and fixed on a rotary shaft; a stationary ring with a sealing face mounted in a casing, which is sealed and axially aligned by means of an elastomeric O-ring, a thrust ring, springs and anti-rotating pins; the sealing face of the stationary ring is pushed into engagement with the sealing face of the rotating ring to form a sealing interface; sealing fluid is located on the high pressure side of the sealing interface; the rotating ring can rotate relative to the stationary ring in bi-direction without contact. The spiral groove groups near the high pressure side are arranged on at least one sealing face of the rotating ring and the stationary ring; the spiral groove groups with segment lands distribute in a circumferential direction; each spiral groove group comprises one radial fluid feed-in groove and at least three rows of spiral grooves with spiral lands arranged in a radial direction; the spiral grooves with spiral lands distribute symmetrically or quasi-symmetrically on the left side and the right side of the radial fluid feed-in groove to form two half groove regions, which can pump the sealing fluid downstream when the rotary shaft and the rotating ring rotate in normal or reverse direction; a non-grooved annular flat dam near the low pressure side is arranged on the sealing face acting as a flow restrict dam and static sealing area. The feature of the hydrodynamic groove pattern on a sealing face according to the present invention can be further described as follows: each spiral groove group is formed by super-imposition of one xe2x80x98Ixe2x80x99-shaped groove, as a fluid feed-in groove, and three or more xe2x80x98xcex9xe2x80x99-shaped grooves, as bi-directional downstream pumping grooves and the whole shape of each groove group resembles a Chinese characterxe2x80x98 xe2x80x99.
The experimental investigations indicate that the performance of the bi-directional dry running gas seals according to the present invention is excellent.
The face seals designed and manufactured according to the present invention can be used for various rotary machines, such as turbo-compressors, turbo-expanders, screw compressors, pumps and agitators, etc.